Effect of 1H-[1,2,4]-oxadiazole-[4,3-α]-quinoxaline-1-one (ODQ), an inhibitor of soluble guanylyl cyclase, on ATRA-induced relaxation of Phe-preconstricted mesenteric arterial rings. Phe-preconstricted mesenteric arterial rings were incubated with ODQ (10−5 M, n = 5) for 30 min and then treated with ATRA (1 × 10−8–3 × 10−6 M) (n = 8 for the ATRA alone). Each value represents the mean ± SE. *P < 0.01 vs. ATRA.